THG's Hurricane Irma (2017)
Hurricane Irma '''Was a devastating, long-lasting and costly category four hurricane that affected parts of the southeast coast. Irma was one of the largest hurricanes on record. Irma caused devastating damage and storm surge to South Carolina, totaling $41 Billion USD, the most damage since Ike of 2008. Hurricane Irma originated from a tropical wave, about 300 miles east of the Lesser Antilles on August 27, moving west-northwest at a moderate speed. Under the influence of a high pressure system, the nascent tropical wave acquired tropical storm strength on August 29. During its infancy, an adjacent upper-level low hindered organization for a time, until it was quickly dissolved by a large Azores high, allowing further organization. The weak tropical storm was designated "Irma" on August 30. On August 31, Irma began affecting the Lesser Antilles and made a very close pass as a category one hurricane, but did not landfall. Heavy rains and up to 80 MPH wind gusts battered Anguilla and subsequent Antigua and Barbuda. Hurricane Irma began to rapidly intensify on the morning of September 2, from a category 1 hurricane with 85 MPH winds to a category 4 hurricane in just 18 hours with winds of 130 MPH. A new steering pattern developed, and Irma continued westward without a trough digging from Canada. On September 3, Irma was marked with an increase in forward speed and accelerated towards the southeast coast. An eyewall replacement cycle ensued, and weakening resulted. On September 4, Irma re-intensified and reached peak intensity with 140 MPH winds. Slight weakening occurred, landfalling as a category four hurricane in South Carolina, with 140 MPH winds and heavy rain. After landfall Irma rapidly weakened and became a tropical storm, and passed over several states as it transitioned to extratropical after September 7, and exited Massachusetts. Irma dissipated a few days later on the 10th. Meteorological History On August 26, a modest tropical wave with rather organized convection was moving west. The disturbance formed from a weak frontal boundary, that originally moved from the Continental United States. Tropical cyclogenesis occurred, and as a result, convection started firing near the newly-formed low pressure, 300 miles east of the Lesser Antilles. The MCHWS gave the disturbance a 70% chance of development over the next two days, and 90% over the next five days subsequently. At 0500 UTC, August 27, a nocturnal burst of convection started to rapidly organize, and the MCHWS assigned the name "Irma". The MCHWS began issuing its first advisories on Irma, at 11 AM EST, August 27. Because of Irma's proximity to the Lesser Antilles, Hurricane Hunters Reconnaissance was sent out to investigate Irma. Dropsondes found a somewhat elongated low pressure center and weak 40 MPH winds, and upper-level dropsonde missions concluded that Irma was being steered by a well-defined Azores high, but also a cold-core low, which was forcing moderate wind shear upon Irma in its infancy. The upper-level low was forecast to dissipate, and allow for Irma to organize and intensify. On August 28, Irma gained fully tropical characteristics and a well-defined, tight circulation and 50 MPH winds, and started moving west-northwest, threatening the northern Lesser Antilles. Another recon mission was sent out at 0000 UTC and dropsondes supported an upgrade to hurricane status, with estimated winds of 80 MPH. Shortly after midnight, Irma made its closest approach to Antigua and Barbuda, heavily impacting both islands as a minimal category one hurricane with hurricane force gusts and heavy rainfall rates. On August 30, Irma began to rapidly intensify north of Puerto Rico. In one of the fastest intensifications in history, Irma underwent a rapid deepening, and strengthened from a category 1 to a category 4 in approximately 17 hours, or a 56 millibar drop. Winds were measured to be 140 MPH. Afterwards, hurricane Irma's forward speed slightly accelerated, and Irma reached peak intensity at 1800 UTC that day. Shortly thereafter, Hurricane Irma underwent an eyewall replacement cycle, and weakened to a category 3. Once Irma's EWRC was complete, the eye enlarged by an extra 20 miles, and the 34 kt wind radii expanded from 150 miles, to 450 miles subsequently. The future track of Irma became increasingly complex, as a rigorous shortwave trough was situated over the Midwestern states, on September 2. The exact strength of that trough was a dilemma for forecasters and especially forecast models, as some predicted Irma would re-curve and spare the southeast coast direct impacts, or slam straight inland to either North Carolina, or South Carolina. On September 3, the trough appeared to be not strong enough, and Irma was forecast to make landfall near Myrtle Beach. Irma's organization began to fluctuate, however, favorable conditions ahead of Irma allowed the storm to restrengthen. On the afternoon of September 4, Irma reached a second, albeit weaker peak intensity of 130 MPH as it made its final approach to South Carolina. At 2:30 AM, September 5, Hurricane Irma made landfall near Myrtle Beach, South Carolina, as a minimal category four hurricane, one of the strongest South Carolina hurricanes since Hurricane Hugo of 1989 to make landfall. As Irma came ashore, Irma rapidly weakened to a tropical storm in 24 hours, dropping heavy rain and high winds. Irma degenerated into a remnant low over eastern Kentucky on September 5, and turned extratropical on September 7 as it moved across multiple states, before emerging off Massachusetts. Irma spawned 5 tornadoes, one of which was deadly at 4:30 PM September 8 in western New York, killing one person. The remnants of Irma degenerated into an open wave frontal system on September 10. Impacts '''Antigua and Barbuda Category:Destructive storms Category:Category 5 hurricanes Category:Costly storms Category:TheHurricaneGod Category:La Nina Year